« ПредишнаНапред »
made up of a countless number of even layers closely bedded together.
From this rock the workmen hew out thick blocks, which are then cleverly split up into flakes or slices of the thickness required, each consisting of one or more of the layers which compose the rock. In some slate rocks these layers are very thin and fine; in others they are thicker and coarser.
Slate is useful to us in many ways. Besides being used to make slates for children, who learn to write upon them, and work their sums upon them, slate is used for the roofs of houses and churches.
Its usual colour is a pleasing dark grey, and is very much liked, for it is soft to the eyes, and never dazzles or strains them when looking at it, except when the sun. shines very brightly indeed upon it.
The pencils with which we write on slates are made of a softer kind of slate than that which we use for writing upon. If they were not, they would scratch your slates, so that you would not be able to rub out the marks.
You can tell me that it is soft; that it is pornus, or full of small holes or cells; you can tell me, that when I dip it in water, it drinks it up quite greedily, as if it were some thirsty animal, and that the water will remain in it, and the sponge be swelled out, till I squeeze it.
When you use the sponge every day to clean your slate, I dare say you do not think about these things, although you may sometimes wonder how a sponge is made, and where it comes from.
You will be surprised, perhaps, to be told, that it took a great many animals a long time to make that piece of sponge in your hand! and that each little hole has, perhaps, held some small creature, which has been turned out of its home to make the sponge useful to you.
No one has ever seen these animals at work, and it is not known whether they make the little cells for themselves, as the bees do their cells, or whether they find them ready formed on the rocks.
The sponges are found under the water (the water of the sea), clinging to rocks. When they are taken up, they are full of little soft things like small pieces of jelly.
Some people think they have seen these little pieces of jelly move, and so they fancy that these are the animals which make the sponge.
When the sponge is first taken from the water, it holds in the little cells-besides the pieces of jelly of which I told you—a great deal of sand and numberless shells.
All these must be carefully picked out, after the sponge has been well boiled. Then the sponge is whitened, by being put into water with chloride of lime. This is the same thing that is used to whiten the pulp in papermaking.
When you have a new piece of sponge, you will find that it is still what you call “ gritty,” or full of sharp pieces of dust.
This dust is really sand. When you wash the sponge before you use it, try to remember, that this sand comes from the bottom of the sea, and that if we could possibly live down there for a few days, we should find—besides sponges—a great many wonderful things as beautiful as the most perfect things that grow and live upon the earth.
BOOKS. “How is a book made ?” “How is it “ printed ?” “How is it sewn to“ gether ?” “How is it bound ?” “How “ can a book be sold so cheaply as it 66 is ?”
Here is a list of questions! We should try to find out all we can about things that are always before our eyes and in our hands.
At one time, books were very rare indeed, for it cost a great deal to make one. Printing was not known, and every word had to be copied by hand.
This took a very long time to do, and the labour cost so much, that a man might buy a piece of ground large enough to build a house upon, for the money a single book would cost him.
It is said that printing was known in England more than 450 years ago. There are three cities which you can find on the map of Europe each of which declares itself to be the first town in which books were printed-Haarlem